Field of the Invention
The present invention relates to a toner for use in electrophotography, electrostatic recording, magnetic recording, etc., and a method for manufacturing a toner.
Description of the Related Art
Due to the cost consciousness and the environmental consciousness which have recently been enhanced, an electrophotographic apparatus such as a copier and a printer is required to be used for a longer period than before. An example of the method for enabling use for a longer period includes filling a toner container with a larger amount of toner, which enhances the convenience for users, giving cost advantages to users through saving resources.
In order to increase the filling amount of toner, however, there exist many problems to be technically solved.
The toner in the container is continuously subjected to agitation for supply of the toner to a developing apparatus. Consequently the toner is subjected to a physical load for a long period. With an increased total amount of toner, an agitation/circulation mechanism in the toner container is required to be upsized and reinforced than before. In this respect also, the physical load applied to the toner increases.
The fluidity of toner is imparted by adding an external additive. In the case of toner subjected to a physical load, however, the external additive is embedded in the toner particle surface, causing a problem that the fluidity of toner decreases. In the case of using an external additive having a small particle diameter, in particular, the fluidity markedly decreases.
Accordingly, many trials have been performed to improve the durability to the physical load applied to toner by using an external additive of an inorganic particle or an organic-inorganic composite fine particle having a large particle diameter, which is more hardly embedded, as described in Japanese Patent Application Laid-Open No. 2000-292972, Japanese Patent Application Laid-Open No. 2005-202131 and Japanese Patent Application Laid-Open No. 2013-92748. The external additives with a large particle diameter, however, has weak physical/electrostatic adhesion to the toner surface due to the size, so as to be easily liberated, causing pollution of various members in an electrophotographic process, which is a problem.
Accordingly, an external additive for use having a large particle diameter is required to have stronger adhesion to the toner surface in comparison with conditions for a conventional external additive having a small particle diameter, so that the conditions for external addition have been widely investigated. In order to achieve stronger adhesion to the toner surface, extension of treatment time has been also investigated (Japanese Patent Application Laid-Open No. 2006-106801). In this case, however, the external additive having a large particle diameter is swept into recesses in the toner particle surface, so that sufficient covering effect of the external additive cannot be obtained.